1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive device having a rotor which rotates based on displacement of a piezoelectric/electrostrictive element or a piezoelectric/electrostrictive device for detecting angular displacement of a rotor with a piezoelectric/electrostrictive element, and a method of driving such a piezoelectric/electrostrictive device, and more particularly to a piezoelectric/electrostrictive device and a method of driving a piezoelectric/electrostrictive device, for use in controlling an actuator for positional control of a hard disk drive (HDD), controlling the angle of a small reflecting mirror, controlling the rotation of an antenna, controlling the θ-axis of an XY stage, and controlling the rotation of a manipulator.
2. Description of the Related Art
Recently, optical, magnetic recording, and precision machining fields have been in need of displacement elements capable of adjusting optical path lengths and positions in a range of submicrons. The development of displacement elements which utilize displacement based on an inverse piezoelectric effect or an electrostrictive effect that is caused when a voltage is applied to a piezoelectric/electrostrictive material such as a ferroelectric substance is under way.
Conventional piezoelectric actuators are problematic in that the movable section thereof moves a small distance because the displacement of a piezoelectric/electrostrictive material as it is expanded or contracted is directly transferred to the movable section.
There has been proposed a piezoelectric/electrostrictive device having a long service life, which can be handled better, allows a component to be mounted easily on the movable section thereof, and can be fixed securely in position. For details, reference should be made to Japanese Laid-Open Patent Publication No. 2002-26411, for example. The disclosed piezoelectric/electrostrictive device permits the movable section to be displaced a large distance under a relatively low voltage applied thereto, allows the device, particularly the movable section to be displaced at a high speed, i.e., at a high resonant frequency. The disclosed piezoelectric/electrostrictive device can provide a displacement element which is not susceptible to harmful vibrations, can respond at a high speed, has high mechanical strength, can be handled better, and is highly resistant to shocks and humidity, and also can provide a sensor element which is capable of detecting movable section vibrations with good accuracy.
When an object is to be moved, there is a demand for moving the object with a rotary motion. For example, perpendicular recording hard disk drives incorporate a magnetic head positioning mechanism which is required to make a rotary motion. The development of a highly responsive fine angle adjustment control device has been expected.
When an object is moved to make a rotary motion, it is preferable to minimize vibrations of the object and to prevent stresses caused by the rotary motion from being transferred to a control system to control the object with high accuracy.